This invention pertains generally to relays which also perform circuit protective functions, such as those used as battery-to-electrical-system contactors in aircraft applications, and in particular to circuit breaker relays which trip open due to an overcurrent condition only after a predetermined period of time-delay.
There have been many circuits designed to be protective from certain conditions after a time delay. One example of such a circuit is Nurnberg et al U.S. Pat. No. 4,042,964, issued Aug. 16, 1977. The circuit there described, however, as well as others, did not provide all of the functions of an overcurrent sensor, a time delay circuit and an undervoltage sensor which control a latching relay which in turn controls a main relay.
Hansen et al U.S. Pat. No. 3,970,908, issued July 20, 1976, discloses the use of a reed switch to perform the function of a current sensor. This design, however, is subject to false indication of overcurrent due to vibration, and is thus unsuited to many applications.
An arrangement of several reed switches oriented at right angles to each other is disclosed in Neuber U.S. Pat. No. 3,471,813, issued Oct. 6, 1969. No means is there disclosed, however, to construct a vibration-resistant current sensor from those reed switches.